Evolution of multiple target‐site resistance mechanisms in individual plants of glyphosate‐resistant Eleusine indica from China

Abstract

BACKGROUND Glyphosate has been used for weed control in South China in various situations for four decades, and most Eleusine indica populations are suspected to have evolved resistance to glyphosate. This research investigated underling target‐site glyphosate resistance mechanisms in six field‐collected, putative glyphosate‐resistant (R) E. indica populations. RESULTS The six R E. indica populations were confirmed to be low (1.8 to 2.6‐fold) to moderately (5.6‐ to 8.4‐fold) resistant to glyphosate relative to the susceptible (S) population. Sixty‐seven glyphosate‐surviving plants from the six R populations were used to examine target‐site resistance mechanisms. Target‐site 5‐enolpyruvylshikimate3‐phosphate synthase (EPSPS) overexpression (OE) (plus further induction by glyphosate treatment) and gene copy number variation (CNV) occurred in 94% R plants, and among them, 16% had the P106A mutation and 49% had the heterozygous double TIPS (T102I + P106S) mutation (plus P381L). In addition, a low number of R plants (6%) only had the homologous TIPS (plus P381L) mutation. The (CT)6 insertion mutation in the EPSPS 5†‐UTR always associates with EPSPS OE and CNV. Progeny plants possessing EPSPS OE/CNV (and P106A) displayed low level (up to 4.5‐fold) glyphosate resistance. In contrast, plants homozygous for the TIPS mutation displayed higher (25‐fold) resistance to glyphosate and followed by plants heterozygous for this mutation plus EPSPS OE/CNV (12‐fold). CONCLUSIONS Target‐site glyphosate resistance in E. indica populations from South China is common with prevalence of EPSPS OE/induction/CNV conferring low level resistance. Individual plants acquiring both the TIPS mutation and EPSPS OE/CNV are favored due to evolutionary advantages. The role of (CT)6 insertion mutation in EPSPS CNV is worth further investigation. © 2021 Society of Chemical Industry.

Challenging glyphosate resistanceEPSPSP106SandTIPSmutations with soybean competition and glyphosate: implications for management

“…Furthermore, this constitutive expression of the TIPS fitness cost has been found to increase up to 85% in a light‐depleted environment driven by competition with rice 17,34 . The results of the present study confirm the inherent TIPS fitness cost 32,34 and reveals that intense soybean competition amplifies the E. indica TIPS fitness cost up to a 95% reduction in vegetative and reproductive growth. Soybean canopy architecture may lead to higher light extinction coefficients compared to other crops such as rice 43,44 .…”

“…The Pro‐106‐Ser EPSPS point mutation (P106S) has been identified in glyphosate‐resistant E. indica 33 . In previous studies, we determined that this target site mutation confers a moderate level of glyphosate resistance (4–8‐fold) with no evident plant fitness cost 3,32–34 . Notably, a rare and unique double glyphosate resistance EPSPS mutation comprising both the Thr‐102‐Ile and Pro‐106‐Ser substitutions (hereinafter termed TIPS mutation) has been identified in E. indica and shown to endow very high‐level glyphosate resistance (113–182‐fold) but with a major plant fitness cost (50–85%) 3,29,30,32,34,35 .…”

“…33 In previous studies, we determined that this target site mutation confers a moderate level of glyphosate resistance (4-8-fold) with no evident plant fitness cost. 3,[32][33][34] Notably, a rare and unique double glyphosate resistance EPSPS mutation comprising both the Thr-102-Ile and Pro-106-Ser substitutions (hereinafter termed TIPS mutation) has been identified in E. indica and shown to endow very high-level glyphosate resistance (113-182-fold) but with a major plant fitness cost (50-85%). 3,29,30,32,34,35 However, estimates of fitness benefit in environments with the joint selection effect of glyphosate treatment and plant competition are lacking and thus our understanding on the rate of enrichment of this glyphosate resistance EPSPS mutations (P106S versus TIPS) is limited.…”

Virtual screening of natural products against 5-enolpyruvylshikimate-3-phosphate synthase using the Anagreen herbicide-like natural compound library

“…22 Glyphosate is known to be one of the main herbicides for E. indica control. 23 The first single resistance mutation P106S was identified in E. indica EPSPS ( Ei EPSPS) two decades ago by Baerson et al 24 The double mutation T102I + P106S was first characterized also in E. indica . 18 It confers a higher level of glyphosate resistance than single mutations at position 106 (such as P106L, P106T, P106A, and T102I).…”

Reduced coenzyme Q synthesis confers non-target site resistance to the herbicide thaxtomin A

“…For example, EPSPS encodes a protein essential for aromatic amino acid biosynthesis which is the target of the herbicide glyphosate (9). Gain of function mutations in the gene encoding 5-enolpyruvyl shikiminate-3-phosphate synthase (EPSPS) resulting from gene amplification (multiple rounds of gene duplication) confers target site resistance to the herbicide glyphosate (10, 11). EPSPS gene copy number is greater in many glyphosate-resistant populations than in glyphosate-sensitive populations, resulting in higher steady state levels of EPSPS mRNA, protein, and total enzyme activity.…”